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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13738) DiskChecker should perform some disk IO
Date Thu, 20 Oct 2016 21:31:58 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15593080#comment-15593080
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Kihwal Lee commented on HADOOP-13738:
-------------------------------------

bq. I don't remember seeing this one yet. Do you have a theory on what causes it?
I think the cause is mainly latent sector error.  As drives getting larger and larger, these
can go unnoticed for long time. Even with the "data_err=abort" mount option, the delayed block
allocation error detected at EXT4 level doesn't normally cause the journal to be aborted (then
become read-only), let alone reacting to read errors. The SMART data (e.g. remapping count)
sometimes correlates to such read errors, but not all the time. I think there is large variance
with manufacturer/model.

> DiskChecker should perform some disk IO
> ---------------------------------------
>
>                 Key: HADOOP-13738
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13738
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Arpit Agarwal
>            Assignee: Arpit Agarwal
>         Attachments: HADOOP-13738.01.patch
>
>
> DiskChecker can fail to detect total disk/controller failures indefinitely. We have seen
this in real clusters. DiskChecker performs simple permissions-based checks on directories
which do not guarantee that any disk IO will be attempted.
> A simple improvement is to write some data and flush it to the disk.



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